A 3-year experiment to evaluate the performance of a number of selected subterranean clover (Trifolium subterraneum L.) lines and cultivars was carried out in grazed hill country pastures in the northern North Island of New Zealand. Seedlings were transplanted into existing swards on easy (15-20° slope) and steep (25-35°s lope) contoured paddocks. Flowering times, spring cover, summer/autumn seedling emergence, and winter plant populations were measured with a particular emphasis on annual regeneration of the lines. Herbage production over the final season and soil seed reserves were also measured. Important factors in the success of subterranean clover genotypes were identified as late maturity, strong autumn regeneration, a long growing season, and prostrate habit. Six lines were identified as performing consistently better than the standard cultivars included in the trial. All have in common a flowering date close to that of 'Tallarook', the ability to regenerate winter plant populations of over 200 plants/m 2 , spring yields of over 1000 kg DM/ha in a mixed sward, and formononetin levels less than 0.15% of dry weight. These lines were therefore considered suitable for further development towards a suitable cultivar for New Zealand summer-dry hill-country pastures.A93066
Three experiments were conducted on hill country at Whatawhata to study the effects of time of oversowing, height of sward cover, treading intensity, chemical treatment of resident pasture, and seed coating on the establishment and early seedling survival after grazing of a number of oversown grasses and legumes. In the environmental conditions experienced, establishment of legumes was higher after spring oversowing; the reverse tended to apply to grasses. All species responded to treading by sheep, especially in mid spring when soil moisture stress was greater. Establishment responses to increasing treading intensity were linear or curvilinear, depending on species, but seedling survival was largely independent of the treading intensity at oversowing. Spraying of resident pasture with maleic hydrazide, paraquat, or glyphosate at the time of oversowing increased seedling establishment at 4 weeks, as well as seedling survival at 8 weeks. Survival, in particular, was directly related to the effect of the chemical in suppressing regrowth of the resident sward for all species except lucerne and lotus. Overall, there was greater response to sward suppression by herbicides than to treading at establishment. An increased seed coat: seed weight ratio increased seedling establishment only slightly.
A nutrient transfer model developed by Saggaret al. (1990) closely predicted the amounts of soil phosphorus (P) (0--150 mm depth) that had accumulated in the soil from fertiliser and excretal inputs in 20 pastoral farmlets grazed by sheep. The 20 farm1ets, located on hill country in the North Island of New Zealand, were grazed by sheep for 8 years (1980--87) with two grazing managements (continuous and rotational). Five rates of single superphosphate (SSP) were applied within each grazing management. The predictions of the transfer model explained 90% of the variations in soil P amounts between farmlets, and 88% of the variations between slope units across all farmlets. However, the model could predict accurately (within 10%
A 3-year trial to evaluate the persistence of a number of selected subterranean clover (Trifolium subterraneum L.) lines and cultivars was carried out in grazed pastures in hill country of the central North Island, New Zealand. Seedlings were transplanted into existing swards on an easy (10-15° slope) contoured paddock. Spring cover, summer/autumn seedling emergence, and winter plant populations were measured, focussing on annual regeneration of the lines. Important factors in the success of subterranean clover genotypes were identified as late maturity and strong autumn regeneration. The recent cultivar 'Karridale' outperformed the well-adapted 'Tallarook'. Five other lines evaluated in this trial stood out in terms of successful persistence and the ability to make a substantial contribution to late winter/spring pasture growth. All had the ability to consistently regenerate winter plant populations in excess of 300 plants/ m 2 , and accumulate buried seed reserves of over 1000 seeds/m 2 . These lines were therefore considered suitable for further development towards a well-adapted cultivar for New Zealand summerdry hill country pastures.
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